Over 600 lawyers have signed a letter criticising a previous letter signed by three former Supreme Court justices that warned Britain may be breaching international law by arming Israel.

The new missive, backed by leading barristers Lord Dyson and Lord Pannick, insists that the UK should not call for an immediate and permanent ceasefire because it would undermine a deal to release hostages held by Hamas.

There is no justification for suspending weapons sales to Israel without evidence of systematic violation of international law by Israel, it adds.

The original letter, sent earlier this week, was backed by over 600 lawyers, academics and retired senior judges.

It said the British government was required by international law to act to secure a permanent ceasefire in Gaza and to suspend the provision of weapons to Israel.

In part, the signatories argued, this is because the International Court of Justice ruled that there was a “plausible risk of genocide in Gaza”.

This is incorrect, however, the new letter contends.

It states: "The court’s ability to issue a provisional measures order depends on a finding that the rights asserted by the party seeking the order are at least plausible.

"It is of course plausible that Palestinians in the Gaza Strip have rights to be protected from acts of genocide. Thus, it is the rights of the Palestinians in the Gaza Strip that were determined to be plausible, and not the alleged commission of genocide against them.”

The letter adds: “Crucially, the court unambiguously confirmed in the same order that it had not been called upon ‘to establish the existence of breaches of obligations under the Genocide Convention’ and that it could not make any definitive findings of fact at this stage.”

The new letter also condemns the signatories of the first letter for going further than the ICJ by suggesting that Britain is obliged to seek a ceasefire to prevent genocide.

"Such an obligation cannot flow from orders that are not binding on the UK and do not impose a ceasefire, and nor can it flow from the Convention itself in the absence of any breach by Israel,” it says.

Jonathan Turner, Chief Executive of UKLFI, which organised the new letter, said: “There are many other errors in the previous letter which we hope to address in the next few days.

"It is indeed regrettable that so many people credulously believe and base their views on the casualty figures fabricated by Hamas, despite their source and in the face of several analyses by statisticians demonstrating their implausibility.”

The exchange of legal opinions comes as increasing pressure is applied to the British government to halt arms sales to Israel following the killing of seven aid workers by the IDF.

Three UK civilians, James Henderson, 33, John Chapman, 57, and James Kirby, 47, were killed after an Israeli drone targeted a humanitarian convoy.

The IDF has suspended senior officials for what it described as a "grave mistake" and said officers believed Hamas militants were travelling in the vehicles targeted.

Conservative MP Flick Drummond told The Guardian: “This has been concerning me for some time. What worries me is the prospect of UK arms being used in Israel’s actions in Gaza, which I believe have broken international law.”

The Labour Party has called for the government to publish its legal advice about whether Israel has broken international law in Gaza.

Lord Ricketts, a former UK national security adviser, has claimed there is now evidence Israel is, “not paying attention to its international humanitarian law obligations.”